This invention describes a method and apparatus for increasing the efficiency and reducing the undesirable emissions of an internal combustion engine. While the general principles and teachings hereinafter disclosed are applicable to all combustion engines, the invention is hereinafter described in detail in connection with its application to a reciprocating, fuel injected, compression ignited, internal combustion engine.
As used herein, the term "conventional engine" refers to a device which converts heat energy, released by the combustion of a fuel, into mechanical energy in a rotating output shaft of the engine. Also, the term "supercharged engine" refers to a conventional engine having the intake air pressurized above atmospheric pressure. Also, the term "disabled cylinder" is defined as having the intake and exhaust valves of one or more cylinders disabled so that they remain closed whether or not the camshaft is rotating. Also, the term "air compressor" is defined as using the engine to take energy from the load driven by the engine to compress air in the engine cylinders and then store it in a reservoir. Also, the term "air motor" is defined as powering the engine by the controlled release of compressed air into the engine cylinders.
In the United States, the law requires that passenger vehicles must be tested over an urban driving cycle and the fuel consumed and exhaust emissions generated determined. This driving cycle has many periods of acceleration, deceleration (including braking) and idle; with few periods of steady state speed. During deceleration and idle operation it is difficult to control emissions in the typical internal combustion engine--particularly throttled engines because of the low manifold pressures at these times. Also, fuel is consumed when the accelerator is released and no energy is required from the engine. The emissions measured during this test must be less than those specified by law at the time of manufacture, and the fuel consumed is used in the determination of the Corporate Average Fuel Economy (CAFE) during that year.
Two of the principle methods of meeting these laws is to reduce the vehicle's size, weight, and aerodynamic drag; and also to utilize computer control of the engine operating variables as described in my earlier U.S. Pat. No. 3,969,614 which is incorporated herein by reference. The present invention uses a controller to control the valve timing and air flow which changes the fundamental operation of the engine in order to reduce fuel consumption and emissions.
Many inventors have proposed using auxiliary equipment to absorb energy from the load during braking and returning this energy to the vehicle driveshaft during accelerations. One of these methods is illustrated in U.S. Pat. No. 3,886,810 (Sugiyama) and embodies a flywheel as the energy storage mechanism. The flywheel and associated control mechanisms are not a part of the fundamental internal combustion engine and the incremental cost and frictional losses of this auxiliary equipment are undesirable. My invention utilizes the pistons, valves, and cylinders of the conventional engine to perform the energy storage and release as well as increasing the efficiency of the engine itself.
Another proposal for saving the kinetic energy of the vehicle utilizes an elaboration of the automatic transmission as shown in U.S. Pat. No. 4,351,409 (Malik). This system uses a transmission modification to couple a hydraulic pump/motor to the driveshaft of the engine and stores energy in a compressed gas cylinder. Once again, the incremental cost and frictional losses of this auxiliary equipment are undesirable and no engine efficiency improvements such as described in my invention are found in this patent.
Another proposal for saving the kinetic energy of the vehicle utilizes a separate air motor coupled to the engine crankshaft through an electromagnetic clutch in U.S. Pat. No. 4,798,053 (Chang). This system causes uncontrolled braking when the accelerator pedal is released, the braking being dependent on the pressure in the storage tank, while my invention stores energy with controlled braking. The only engine efficiency improvement in this patent is the stopping of fuel flow when the accelerator is initially released, but the engine idles when the vehicle stops. My invention uses no fuel unless the accelerator is depressed and has other significant fuel savings.
A proposal for controlling the engine valves to improve the operating efficiency of the engine is found in U.S. Pat. Nos. 5,284,116, 5,123,397, and 4,945,870 (Richeson). This system controls the opening and closing times of electric intake and exhaust valves of an engine for the purpose of improving the cylinder burn conditions. It does not utilize any vehicle kinetic energy as described in my invention, nor does it disable valves to operate a multi-cylinder engine on less than all the cylinders such as described in my invention.